1. Technical Field
The present invention relates to a blank material to be cut for dentistry, a metal powder for powder metallurgy, a metal frame for porcelain fusing for dentistry, and a dental prosthesis.
2. Related Art
In order to replace crown defects or tooth defects during a dental treatment, crowns, bridges, or artificial teeth are widely used. Among these, from the viewpoint of aesthetics and functionality, a dental prosthesis in which a ceramic material called porcelain is fused to the surface of a metal frame is used.
In JP-A-11-1738, a precious metal-based alloy for a metal frame in which metal elements such as Sn, Ga, and In are added to metal elements such as Au, Pd, Cu, Ir, and Ag is disclosed. This alloy can be molded into a desired shape by a casting method. Therefore, by fusing crown restoration porcelain to the surface of the metal frame made of the alloy, a dental prosthesis having excellent aesthetics can be obtained.
Recently, a method of forming a metal frame on the basis of shape data obtained by measuring the three-dimensional shape of an affected area has become more common. The mechanism used in this method is called a dental CAD/CAM system. CAD (computer aided design) is a system which acquires the three-dimensional shape of an affected area using a 3D scanner or the like and digitizes the shape. In addition, CAM (computer aided manufacturing) is a system which cuts a processing object on the basis of the numerical data generated by CAD to be machined into a frame having an appropriate shape for the affected area. The dental CAD/CAM system which has the combined systems can easily realize high dimensional accuracy that does not intricately depend on the skill of a dental technician according to the related art and thus can efficiently form a metal frame having excellent compatibility with the affected area. Accordingly, further spreading of the system is expected (for example, refer to JP-A-2007-215854).
The processing object provided for the dental CAD/CAM system is generally called a “blank” or “blank material”. The blank material requires machinability in addition to properties desired for a metal frame including aesthetics, compatibility with a living body, chemical stability, and wear resistance. Machinability is the ability to be properly cut, and by using a blank material with good machinability, a metal frame which is accurately reproduced in a desired shape can be efficiently machined by the CAM on the basis of numerical data generated by CAD.
The alloy described in JP-A-11-1738 is an alloy appropriate for the casting method but has a problem of degraded machinability. In a case where the machinability of the blank material is poor, the intended processing cannot be performed, and a difference occurs between a shape after the processing is complete and the desired shape. As a result, effort for secondary processing to modify the as-processed shape is needed. In addition, since compatibility with the affected area is low, there is a problem in that a patient may sense the incompatibility.